The present invention relates to an optical field enhancement device with a fine metal structure capable of inducing localized plasmon and a manufacturing method of the same.
Field enhancement devices, such as sensor devices, Raman spectroscopy devices, and the like, that utilize a field enhancement effect of a localized plasmon resonance phenomenon on a surface of a metal are known. The Raman spectroscopy is a method of obtaining a Raman scattered light spectrum (Raman spectrum) by separating scattered light obtained by illuminating single wavelength light onto a substance, and it is used for identifying a substance or the like.
Raman spectroscopy includes a method that utilizes an optical field enhanced by localized plasmon resonance, called surface enhanced Raman scattering (SERS), to enhance weak Raman scattered light (refer to S. Ghadarghadr et al., “Plasmonic array nanoantennas on layered substrates: modeling and radiation characteristics”, OPTICS EXPRESS, Vol. 17, No. 21, pp. 18556-18570, 2009). This makes use of the principle that when light is illuminated onto a metal body, in particular, onto a metal body having a nano-order uneven pattern on a surface with a substance being in contact with the surface, optical field enhancement occurs due to localized plasmon resonance and the intensity of Raman scattered light of the sample in contact with the surface of the metal body is enhanced. The surface enhanced Raman spectroscopy may be performed using a substrate having an uneven metal structure on a surface as a carrier (substrate) for carrying a subject.
As for substrates having metal fine uneven structures on a surface, a substrate manufactured by forming an uneven pattern on a surface of a Si substrate and forming a metal film on the surface of the uneven pattern is mainly used (refer to PCT Japanese Publication No. 2006-514286, Japanese Patent No. 4347801, and Japanese Unexamined Patent Publication No. 2006-145230).
Further, a substrate manufactured by anodizing a surface of an Al substrate to turn a portion into a metal oxide (Al2O3) layer and filling a metal in a plurality of fine pores spontaneously formed in the metal oxide layer during the anodizing process and opens at the surface of the metal oxide layer is also proposed (refer to Japanese Unexamined Patent Publication No. 2005-172569).